The ELI-GBS LINAC, designed to accelerate electrons up to 800 MeV, employs 23 quadrupole and 2 dipole magnets for beam focusing, steering and bending toward two diagnostic lines. Factory and laboratory measurements confirmed that both magnet types meet design specifications, with quadrupoles achieving high field homogeneity and dipoles exceeding integrated bending field requirements while maintaining uniformity within plus or minus 10^-3. Comparative tests highlighted minor differences due to measurement methodology but validated operational performance. Following delivery, the magnets were installed in the LINAC lattice with alignment corrections applied to ensure beam optics stability at the target energy. Complementary magnetostatic simulation provided a consistent model of the dipole geometry and excitation, demonstrating the integration of experimental and computational approaches for magnet characterization and installation verification in support of reliable accelerator operation.

The ELI-NP (Extreme Light Infrastructure – Nuclear Physics) Gamma-ray Beam Source (ELI-GBS), currently under construction, employs an 800 MeV linear accelerator (LINAC) to generate high-brightness gamma rays through laser–electron interactions. Its control system is designed as a distributed, EPICS-based architecture, where engineering-level control is provided for devices such as LLRF, modulators, magnets, profile monitors, and current monitors. A set of high-level application tools is required for LINAC beam commissioning, tuning, and the measurement of key accelerator parameters. To meet the beam diagnostic capabilities and performance requirements of the commissioning process, we have developed Python-based high-level application software to support essential commissioning tasks, including gun phase scans, emittance measurements, and beam energy measurements. The software uses the pyepics package to interface with engineering-level device IOCs. To support visualization and offline simulation, a set of Python soft IOCs has also been implemented, enabling realistic emulation of device behavior and data acquisition workflows. The online measurement capabilities of the system will be validated during the upcoming RF Gun commissioning and the subsequent LINAC commissioning phases.

The RF linac for the ELI - Gamma Beam Source (ELI-GBS) is being installed in Bucharest-Magurele (Romania). TW accelerating structures and SLED cavities are powered by klystrons via waveguide network that includes directional couplers for power monitoring and feedback. Before RF conditioning can begin, the linac must be properly tuned in terms of the RF phase and frequency. The waveguide system was reviewed with respect to its electrical length to ensure correct RF phase tuning. This work was carried out after installation but prior to connecting the waveguides to the accelerating structures. Fine RF-phase adjustments will be achieved through mechanical deformation of the waveguides. Since each klystron feeds four structures, the waveguides must be tuned so that the RF phase at the entrance of each structure matches its longitudinal position in the accelerator. Considering the fact that only 5-degree deviation in phase can be compensated by mechanical deformation of waveguides, larger discrepancies must be corrected physically by bending existing waveguide components to correct position or even reposition accelerator segments. Therefore precise analysis of the waveguide network was performed using a network vector analyzer. This paper reports the results of phase measurements performed on the assembled waveguide system. In addition, directional couplers were individually tested with VNA to verify their performance before integrating them into the system.

The high brilliance ELI – Gamma-ray Beam System (ELI-GBS) is under implementation at Extreme Light Infrastructure - Nuclear Physics (ELI-NP) in Romania. The system uses an 800 MeV S-band accelerator driver as an Inverse Compton Scattering (ICS) source coupled to an interaction laser and in the future to a high-finesse optical cavity. The γ-ray beam will be available with energies up to 19.5 MeV to drive an ambitious scientific program which requires high spectral density (larger than 5×10^3 photons/s/eV), narrow bandwidth of 0.5%, and linear polarization higher than 95%. The ELI-GBS is foreseen to be finalized in an initial configuration in 2026. Details of the status of the LINAC, interaction laser system, and challenges for completing the system will be highlighted.